Fast calculation methods
Addition Add 137,95 Solution: = (137-5)+100= = 232
addition Add Solution = (100-3)+(100-5)+(100-2)+(100-6)+(100- 7)= (500-23)=477
Multiplication
Multiplying by 5 Example: Find the result of 324*5 Solution: 324*5= 324*(10/2)= (324/2)*10 =1620
Multiplying by 11 Example: Find the result of 35*11 Solution * 385 +
Other multiplication methods Find the result of: 49*51 Solution 49*51= (50-1)*(50+1)= (50^2)-(1^2)= = 2499
Other multiplication methods Find the result of: 57*53 Solution 53 * 57 * 1 + * 3021
Squaring Square the number: 53 Solution 53 ^ ^2
Squaring Square the number: 46 Solution 46 5^ ^2 10-6
Division
Division by 5 Find the result of: 147/5 Solution 147/5= 147/(10/2)= (147*2)/10= 294/10= 29.4
Average of 3 numbers Find the average of: 89,91,95 Solution: ( )/3= ( )/3 ( )/3+2/3= 91.66
Division by 7 1/7= 2/7= 3/7= 4/7= 5/7= 6/7=
Division by 7(continued) From the previous slide: Each fraction has the same floating point numbers with the same sequence but with different fraction beginning. The next slide arranges the fraction
Arranging fraction 1/7= 3/7= 2/7= 6/7= 4/7= 5/7= The numerator {1,3,2,6,4,5} is the same with the sequence generated from the modular equation 3 x n mod 7 and x 0 =1
Example Find the result of 102/7 Solution: 102/7= (98+4)/7= 14+(4/7)=